Gas sensor characteristics for smoldering fire caused by a cigarette smoke

It was attempted to detect a smoldering fire which was mainly caused by a cigarette in a general house. Same types of eight sensors are adopted in this experiment to detect the fire. The sensor is a type of a tin oxide gas sensor which is used to detect various kinds of reducing gases. It is on a market as a gas detector. The sensor is mounted at a supporting bar and its height can be changed. The height was set at 50, 100 and 150 cm in the experiment. The lit cigarette was put on a cotton cloth and the generated gases were detected. The cloth was adopted as a subjective material for the fire. The sensor output near the fire source fluctuates largely. It was attempted to identify the position and burning material of the fire. The moving average characteristics of the sensor outputs were derived and the differential characteristic of the sensor output was also derived. The characteristics are effective to identify the fire position. The scattering diagram for two sensor outputs near the fire source was introduced and the slope of the characteristic was derived. The slope is effective to distinguish the material of fire source. As for the result, it can be distinguished the fire position within about 30 s and fire material roughly. Tin oxide gas sensor is good for detecting the smoldering fire.